This invention relates to a chair that effectively improves comfortability to sit on with a simple arrangement.
For a chair whether it is comfortable to sit on or not is one of major factors affecting a body of a seated person or a working efficiency and this is the most important fundamental function as a chair. Then chairs have been highly functioned in a multilateral manner to improve comfortability to sit on through varieties of mechanisms such as backrest reclining, back and seat rocking or lumber support.
Viewed from a point of a lumber support function, there have been some lumber support functions that can adjust a position of the lumber support. A position of a lumber of a human or a way to sit differs depending on individual specificity such as a gender, an age, or physical attributes. Then that a position of the lumber support can be adjusted is very effective especially for a chair manufactured in a standardized manner in terms of fitting the chair to varieties of users.
A conventionally conceived mechanism is superior functionally, however, it is complicated such that a lumber support member is embedded inside the backrest movably in an operable manner from outside and then the lumber support member is operated so as to push the backrest, which makes a face of the backrest projected or depressed.
Due to this arrangement, it is difficult for a simple-type chair to adopt the mechanism unless the chair has an arrangement in which backrest is thick enough to allow increment of a member of the mechanism to be embedded.